From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from conssluserg-06.nifty.com ([210.131.2.91]:17761 "EHLO conssluserg-06.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726078AbeJHVpG (ORCPT ); Mon, 8 Oct 2018 17:45:06 -0400 MIME-Version: 1.0 References: <20180921142234.16882-1-kieran.bingham+renesas@ideasonboard.com> <20181005083313.2088252-1-arnd@arndb.de> <5cbb504c-0506-cec8-d51b-00928cdb27fe@ideasonboard.com> In-Reply-To: <5cbb504c-0506-cec8-d51b-00928cdb27fe@ideasonboard.com> From: Masahiro Yamada Date: Mon, 8 Oct 2018 23:32:06 +0900 Message-ID: Subject: Re: [PATCH] kbuild: fix kernel/bounds.c 'W=1' warning To: kieran.bingham+renesas@ideasonboard.com Cc: Miguel Ojeda , Arnd Bergmann , Andrew Morton , Linux-Renesas , stable , Linux Kernel Mailing List , Linux Kbuild mailing list Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-renesas-soc-owner@vger.kernel.org List-ID: On Mon, Oct 8, 2018 at 7:01 PM Kieran Bingham wrote: > > On 06/10/18 23:06, Masahiro Yamada wrote: > > On Sun, Oct 7, 2018 at 6:58 AM Masahiro Yamada > > wrote: > >> > >> Hi Miguel, > >> > >> > >> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda > >> wrote: > >>> > >>> On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann wrote: > >>>> > >>>> Building any configuration with 'make W=3D1' produces a warning: > >>>> > >>>> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmi= ssing-prototypes] > >>>> > >>>> When also passing -Werror, this prevents us from building any > >>>> other files. Nobody ever calls the function, but we can't make > >>>> it 'static' either since we want the compiler output. > >>>> > >>>> Calling it 'main' instead however avoids the warning, because gcc > >>>> does not insist on having a declaration for main. > >>> > >>> I think marking the function as static __used should do the trick and > >>> would be less confusing. > >> > >> > >> > >> > >> I tried __used, but I still see the warning. > >> > >> > >> masahiro@grover:~/ref/linux$ git diff > >> diff --git a/kernel/bounds.c b/kernel/bounds.c > >> index c373e88..aee0101 100644 > >> --- a/kernel/bounds.c > >> +++ b/kernel/bounds.c > >> @@ -13,7 +13,7 @@ > >> #include > >> #include > >> > >> -void foo(void) > >> +void __used foo(void) > >> { > >> /* The enum constants to put into include/generated/bounds.h *= / > >> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS); > >> masahiro@grover:~/ref/linux$ make W=3D1 prepare > >> CC kernel/bounds.s > >> kernel/bounds.c:16:13: warning: no previous prototype for =E2=80=98foo= =E2=80=99 > >> [-Wmissing-prototypes] > >> void __used foo(void) > >> ^ > >> CC arch/x86/kernel/asm-offsets.s > > > > > > > > Sorry, I forgot to add 'static'. > > > > Adding both static and __used worked for me, > > and I like the idea. > > > > Aha - I'd also tried converting to static in my earlier attempts, but > didn't realise we had __used! > > updating as "static __used" causes the following diff: > > diff -Nurp bounds.s.foo bounds.s.static-used > --- bounds.s.foo 2018-10-05 10:20:53.269941404 +0100 > +++ bounds.s.static-used 2018-10-08 10:51:18.079309049 +0100 > @@ -110,7 +110,6 @@ > #NO_APP > .align 2 > .p2align 3,,7 > - .global foo > .type foo, %function > foo: > stp x29, x30, [sp, -16]! //,,, > > > I'd say this is a pretty good alternative fix - however I see Arnd's > version is already on it's way though akpm's tree... > > https://ozlabs.org/~akpm/mmots/broken-out/kbuild-fix-kernel-boundsc-w%3D1= -warning.patch > > Anyway, as long as one of the variants gets there I'll be happy :) I will leave it to Arnd. When we fix arch/{mips,sparc}/kernel/asm-offsets.c, 'static __used' is just additions. The 'main(void)' solution would require a little bit restructuring. FWIW, with my quick analysis, the following should be fixed as well: arch/alpha/kernel/asm-offsets.c arch/c6x/kernel/asm-offsets.c arch/ia64/kernel/asm-offsets.c arch/ia64/kernel/nr-irqs.c arch/mips/kernel/asm-offsets.c arch/riscv/kernel/asm-offsets.c arch/sparc/kernel/asm-offsets.c arch/x86/kernel/asm-offsets.c arch/x86/um/shared/sysdep/kernel-offsets.h samples/bpf/syscall_nrs.c --=20 Best Regards Masahiro Yamada